By Andrew & Joanna

Global Water Supply 97.4% of the Earth’s water is salty Most of the remaining 2.6% of fresh water is not readily available to humans; trapped as ice in polar caps. Only 0.014% of global water supply is readily available to humans and other life forms. Recycling is therefore important to maintain this supply of water

The Water Cycle The water cycle involves evaporation and precipitation. Although most of the evaporated water returns directly to the sea some of it falls in rivers and lakes etc and can be used by humans.

Increasing Demand for Water Agriculture: 73% Industry: 22% Domestic Usage: 5% As technology and world population increases, the need for more water also increases and water is becoming more and more a limiting factor.

Meeting the Increased Demand As the need for more water increases, water management techniques must be efficient at keeping water consumption to a minimum. About 90% of water from industrial and domestic usage can be returned to waterways and reused if managed carefully.

Effective techniques to Manage Water Consumption Micro Irrigation: This new technique uses perforated pipes to “drip feed” crops with water, thus only using necessary volumes of water. Dams: Allows slight control over the water cycle and provides sufficient water for a specific area. Also prevents flooding. However irrigation channels may carry deadly parasites and malaria carrying mosquitoes may breed in the shallow waters.

Unpredictability of Supply In Developed countries there is normally a continuous supply of clean and safe water Many developing countries cant depend on a reliable source of water; some regions have a permanent shortage of water and in others rainfall is random and erratic. The world’s water supply is unevenly distributed

Climate The climate of a region is the result of interactions between the atmosphere, land mass, oceans and geographical locations of the region. The climate of a region changes over time and can affect the availability of the water supply to the area.

Short Term Climate Change Brief, extreme changes in a regions climate occur occasionally. These short-lived changes can have devastating effects on the region.

Erosion Erosion is the loss of the fertile top soil by the action of water or wind on the land. Erosion rarely occurs in areas well covered by vegetation. Erosion can be prevented on farmland by building terraces to grow rice and by ploughing sloping fields round the contours of hills.

Deforestation The complete clearing away of a forest. The destruction of these areas can have terrible effects on the water cycle.

Effects of Deforestation on Water Cycle Effect of deforestation Consequence Loss of forest’s “sponge” effect; flow of water no longer regulated. Erosion of top layer of soil by fast moving water. Less water vapour returned to atmosphere by evaporation. CO 2 produced during burning of the forest. Rivers fail to supply consistent supplies of water needed by humans or flooding of low- lying areas. Soil fertility reduces; rivers and lakes become blocked with silt; water becomes undrinkable. Reduction in rainfall so climate becomes drier. Extra CO2 may contribute to the “green-house effect”

Desertification There are many area of the world covered by desert. When it is caused by human actions it is named desertification.

Desertification